(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: To compare three different methods of optimizing dose distributions of target volumes and normal tissues during stereotactic body radiation therapy (SBRT) for pancreatic cancer proposed by Blanck (Blanck, et al. Inverse treatment planning for spinal robotic radiosurgery: an international multi-institutional benchmark trial. JACMP, 2016), Li (Li T, et al. A method to improve dose gradient for robotic radiosurgery. JACMP, 2015) and Cao (Cao Y, et al. Optimization of dose distributions of target volumes and organs at risk during stereotactic body radiation therapy for pancreatic cancer with dose-limiting auto-shells. Radiation Oncology, 2018).
Methods: Twenty-five cases of pancreatic cancer were retrospectively analyzed. Treatment plans were optimized with these three methods by three-step optimization with 1 collimator and 4 shells proposed by Blanck, two-step optimizations with 2 collimators and 7 shells proposed by Li and one-step optimization with 1 collimators and 7 shells proposed by Cao. The conformity index (CI), new conformity index (nCI), homogeneity index (HI), gradient index (GI), coverage, dose-volume and doses to organs at risk were compared.
Results: The CI, nCI, GI, volumes encompassed by 100%, 50% and 30% isodose lines significantly decreased while coverage, volumes encompassed by 10% isodose lines, the number of beams, monitor units and treatment time significantly increased if calculated with Li’s method. Additionally, in Cao’s method, the D10cc of the stomach, D5cc and D10cc of the duodenum significantly decreased. Moreover, the Dmax of the intestine significantly decreased with Blanck’s method.
Conclusion: Better dose distributions of target volumes were accessible by two-step optimizations with 2 collimators and 7 shells with Li’s method. Lower radiation doses to OARs were accessible by one-step optimization with 1 collimators and 7 shells with Cao’s method.
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